The disclosure relates to an axial piston machine with hydrostatic relief of its pivot cradle.
In the case of axial piston machines with a swashplate design, piston feet are coupled to a pivot cradle which is pivotable in respect of a housing, in order to adjust the stroke volume. For this purpose, slide bearings are provided in arc form between the fixed or stationary housing and the movable pivot cradle.
The working pressure of the cylinder/piston combinations concerned give rise to high supporting forces which are transferred from the pistons via the piston feet to the pivot cradle and which have to be transferred to the housing via the slide bearing. For this purpose, a slide bearing is usually provided in each case on both sides of a central drive shaft on the pivot cradle, wherein the slide bearing assigned to the high-pressure side has to bear substantially higher supporting forces than the slide bearing assigned to the low-pressure side. So that these high supporting forces can be partially compensated, it is known from the state of the art for hydrostatic relief to be provided in the slide bearing concerned or in the two slide bearings.
The hydrostatic relief mainly has recesses or cavities which may, in particular, be formed on the convex bearing faces on the pivot cradle side or on the concave bearing faces on the housing side. The recesses are supplied with relief pressure medium via pressure medium channels on the housing side or the pivot cradle side.
Publication DE 37 24 285 C2 discloses an axial piston machine with a pivot cradle bearing which has a slide bearing shell on the housing side. This extends integrally on both sides of the drive shaft. On each side of the slide bearing shell are provided two relief grooves which are parallel to one another. These are supplied with relief pressure medium separately from one another and successively in time. The pressure medium is supplied via bores which are on the pivot cradle side and therefore are moved relative to the fixed or stationary relief grooves.
Publication DE 10 2011 121 523 A1 shows hydrostatic relief in the form of a zigzag-shaped relief groove which extends via a central region of the bearing face on the pivot cradle side. The relief groove is supplied with relief pressure medium via a supply channel likewise running through the pivot cradle.
It is furthermore known in the art for even larger pressure fields to be formed as hydrostatic relief.
Publication DE 10 2012 214 830 A1 shows relief recesses which are delimited via their edge contours, whereby relief pressure fields are defined. The disadvantage of this is that the relief recess is not available as a supporting bearing face of the slide bearing.
This disadvantage is offset by publication U.S. Pat. No. 4,710,107. FIG. 2 shows a circumferential closed relief groove which is supplied with relief pressure medium via two bores which open directly into the groove.
Publication DE 21 01 078 also offsets the disadvantage of the bearing faces which are made significantly smaller by the relief pressure fields. FIG. 2 shows a closed relief groove in the form of an angular eight which is supplied with relief pressure medium via a central bore opening directly into the groove.
In the case of the two aforementioned publications, the same pressure will prevail overall following a sufficiently long operation, even in the region or regions within the circumferential relief groove. During actual operation, reduced relief pressure will prevail in the middle of the region or in the regions between the relief groove.
The disadvantage of the hydrostatic relief in the two aforementioned publications is that the relief grooves arranged at right angles to one another are difficult to produce. In the case of production using a disk-milling cutter, for example, this must be pivoted through 90°. In particular, it is difficult to produce the two connection grooves on the short sides of the relief pressure field or the two relief pressure fields using a disk-milling cutter, as this must also be positioned obliquely due to the curvature of the bearing face in addition to the pivoting.
By contrast, the disclosure is based on the problem of creating an axial piston machine in which the aforementioned production disadvantages are avoided in respect of the hydrostatic relief.